Who caused him to die? "Flame eyed golden eyes" uncover the truth, male corpse fibers are revealed on the roadside | form | truth

"Sometimes the clues we encounter may seem like nothing, but under instruments such as microscopes and infrared spectrometers, even a single fiber cannot escape its' golden eye '. Recently, judicial expert Sun Qiran revealed to a reporter from the Legal Daily that she used her secret weapon to discover evidence and help the police solve cases.".

At the Traces and Trace Evidence Appraisal Laboratory of the Judicial Appraisal Science Research Institute, Sun Qiran has been dedicated to operating various testing instruments for a long time, searching for clues to solve cases in those small and delicate test materials.

"Our job nature is quite unique, and most of it is conducted in the laboratory. Our leaders often told us before that when doing trace evidence identification, we should be able to sit still and endure loneliness," said Sun Qiran.

After 11 years of training, Sun Qiran has handled hundreds and thousands of cases, and has become a senior engineer in physical evidence. "Our test results are often the key to determining the nature of the case," she recalled the traffic accident and escape case that occurred in Guyuan City, Ningxia Hui Autonomous Region in 2020.

At 23:28 on May 27, 2020, in the dead of night, a Dongfeng brand heavy-duty fence truck loaded with rock wool colored steel plates was driving on the 1613 kilometer 634 meter section of the 327 Liangu Line

At about 6:20 the next morning, the police received a report from the masses that a male corpse was found in the road section, which was suspected to have died in a traffic accident, but there was no vehicle involved in the accident, let alone the suspect.

Since then, although the police quickly locked a suspect car, and deployed control all the way, they found the car at a construction site in a neighboring town, but because there was no monitoring and no witnesses at the crime scene, how to confirm the criminal facts and suspect became a thorny problem.

After on-site investigation, the police extracted a small cloth strip measuring 3 centimeters long and 2 centimeters wide from the carriage of the suspected vehicle, and hoped to find key evidence to solve the case on this small cloth strip.

If the incident is urgent, the murder case will be solved. On May 29th, the third day of the incident, the police brought a cloth strip and a black jacket from the deceased to the Judicial Yuan to seek help. Sun Qiran took over the case.

"In traffic accident and escape cases, it is necessary to do trace evidence identification." Years of work experience have made Sun Qiran understand the importance of this case, and she also knows that there is not much time for herself. She quickly got into work.

Taking photos and numbering the jackets and small cloth strips is the first step of Sun Qiran's work. During this process, she noticed that the small cloth strip provided by the police was clearly a lining of a piece of clothing, interwoven with brown and blue yarn, embroidered with letters on the blue yarn, and with white flocculent material on the other side, seemingly filling cotton inside the lining.

She carefully inspected the lining of the jacket again and indeed found a hole on the right side. "However, no bloodstains or other evidence related to the case were found on the jacket and small cloth strips. What is the connection between the two? Only through trace evidence identification can it be finally determined."

Sun Qiran cut off a small piece of cloth about the size of the jacket lining and strip, and used it as a comparison sample. "First, we need to classify the lining and filling cotton materials into the same category, then inspect their respective forms, and finally analyze whether their fiber composition is consistent." Sun Qiran described the entire process of trace evidence identification to the reporter in just a few words.

So she first separated the white flocculent material from the fabric, and then separated the blue and brown interwoven warp and weft lines on the fabric. They were inspected for their morphology using a biological microscope. After confirming that the warp and weft lines on the fabric were of the same morphology, she compared the morphology of the colorless, blue, and brown fibers in the test material and sample jacket, confirming that the morphology of the different colored fibers corresponded to each other. She began analyzing the composition of a single fiber.

Infrared spectrometer is an indispensable component detection instrument. Through inspection, she found that the brown and blue fibers in the test material and sample strips are polyester fibers, and the colorless filling fibers are cotton fibers.

However, unlike biological microscopes, infrared spectrometers are unable to compare the color composition of the test material and sample fibers. That is to say, although the morphology and composition of the three different colored fibers correspond to the same, and the appearance colors are similar, is the color composition of the fibers really consistent? If it is impossible to confirm that the color of the test material and sample fibers is consistent, the identification result cannot determine that the two are of the same type of fiber.

So she used a laser micro Raman spectrometer to compare the colors of blue fibers and brown fibers, and found that the Raman spectra of the sample fiber color were consistent. At this point, the fiber morphology, composition, composition, and color of the cloth strips extracted from the suspect vehicle are completely consistent with those on the deceased's jacket. Sun Qiran concluded that the jacket lining and the small cloth strips belong to the same material, which means that the small cloth strips extracted from the suspect vehicle were hooked and pulled from the jacket lining worn by the deceased at the crime scene. A week later, based on the appraisal results, the police determined the vehicle and driver involved, Li.

"The identification of colored fibers has always been a difficult point in trace evidence identification. Previously, spectrophotometry was used to detect the color of fibers, and the detection results were affected by many factors, such as the angle of the light source, the degree of fiber distortion, and whether it was contaminated. These factors can affect the identification results." Sun Qiran told reporters, "Our team has explored and summarized through practice and scientific research, and applied laser micro Raman spectrometer to find a solution to the identification problem of colored fibers. After the technology is mature, a report has been submitted to the Ministry of Justice, promoting the establishment of a relevant ministerial technical standard 'Comparison Inspection of Single Fiber - Laser Micro Raman Spectroscopy'."

"Do you feel particularly proud that your exploration has been recognized by the industry?" the reporter asked.

"In addition to forensic appraisal, we have also been exploring the blank areas of forensic science, developing new technologies for scientific appraisal, and 'defending justice with science'. This is the mission of the Judicial Yuan personnel." Sun Qiran replied.